Finned tube, apparatus and method for making same



y 26, 1966 B. M. WOLOSZYNEK 3,262,295

FINNED TUBE, APPARATUS AND METHOD FOR MAKING SAME Filed July 20, 1961 2 Sheets-Sheet 1 IN VEN TOR.

B OL ESLAW M. WOLOSZ YNE K \IllllllIl/Illlllll '11 QA v F I v 7flni" July 1966 B. M. WOLOSZYNEK 3,262,295

FINNED TUBE, APPARATUS AND METHOD FOR MAKING SAME Filed July 20, 1961 2 Sheets-Sheet 2 IN VEN TOR. BOLESL AW M. WOLOSZ YNE K United States Patent 3,262,295 FINNED TUBE, APPARATUS AND METHOD FOR MAKING SAME Boleslaw M. Woloszynek, 1125 Willaview Road, Cleveland, Ohio Filed July 20, 1961, Ser. No. 125,584 17 Claims. (CI. 7275) My invention relates to a metal tube having a helical fin formed thereon by rolling, to the apparatus and to the method for making the same.

An object of my invention is to provide a metal tube with a helical fin formed thereon and having a metallic grain structure of improved characteristics.

Another object is the provision of improved apparatus for the forming of a helical fin on the outer cylindrical wall of a metal tube.

Another object is the provision of an improved method for forming a helical fin on the outer cylindrical wall of a metal tube.

Another object is the provision for advancing a tube having a helical fin formed thereon by auxiliary means.

Another object is the provision of auxiliary means to feed a tube forwardly intermediate fin-forming elements, which auxiliary means adapts itself to the forward movement of the tube permitted by the elements.

Another object is the provision for so feeding a tube along rotating fin-forming elements that working and graining distortion of the metal in the fin is minimized or avoided.

Another object is the provision for regularity and symmetry in the metal grain structure of the fin rolled upon a metal tube and to the wall of the tube from which the fin protrudes.

Another object is the provision for maintaining the tube in straight cylindrical alignment following the fin-forming operation on the outer wall of the tube.

Another object is the provision for truing the internal cylindrical bore of the tube during the fin-rolling operatron.

Another object is the provision of an improved finned tube by means not heretofore known.

Another object is the provision for producing a superior finned tube in an efiicient and economical manner.

Another object is the provision of a finned tube having improved internal structural characteristics.

Other objects and a fuller understanding of my invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a longitudinal sectional view of apparatus embodying my invention, in which the parts are in one relative position (the view of FIGURE 1 is taken along the line 11 of FIGURE 3);

FIGURE 2 is a longitudinal sectional view of said apparatus embodying my invention, in which the parts are in another relative position;

FIGURE 3 is an end view of the apparatus shown in FIGURE 1 looking in the direction of the arrows 33 of FIGURE 1;

FIGURE 4 is a magnified view of a section of tube and showing a fin formation thereon, the view of FIGURE 4 illustrating a section of tube and fin made in the usual manner without the use and benefit of my invention, and is shown for comparative purposes; and

FIGURE 5 is a magnified sectional view of a tube showing a fin formation thereon, the view of FIGURE 5 illustrating a section of the tube and fin made in accordance with my invention and illustrating the superior structure obtained by the use of my invention. 7

With reference to the views of the drawing, my said apparatus includes three fin-rolling elements denoted generally by the reference characters 11, 12, and 13. The fin-rolling elements are each composed of an arbor 14 upon which a plurality of toothed disks of circular shape are mounted next to each other and held in position by a nut and washer assembly 16. The outer peripheral edges of the plurality of disks 15 are formed to press into the metal of a metal tube and upon rotation of the rolling elements about their respective axes forming a helical fin integral with the tube. The fin is formed by the outward flow of metal in the spaces between the several disks 15.

The three fin-rolling elements 11, 12, and 13 are spaced apart relative to each other, as illustrated in FIGURE 3, so as to accommodate a tube intermediate of the elements 11, 12, and 13. The axes of the elements 11, 12, and 13 are generally parallel to the axis of the tube but not completely parallel in that it is usually provided that there is a small acute angle between the axis of each element and the axis of the tube.

A rotatable sleeve member 17 is positioned to support the tube and to guide the tube through a path intermediate of the fin-rolling elements. This rotatable sleeve member has a gear 18 connected thereto so that rotative driving of the gear 18 rotates the sleeve member 17 about its axis. A source of power, such as the motor 19, is connected by a driving connection 20, shown diagrammatically by a broken line, between the motor 19 and the gear 18. The driving connection 20 also connects to and rotatably drives the arbors 14 of the three elements 11, 12, and 13. Therefore, as the fin-rolling elements are rotated during the fin-rolling operation, the supporting sleeve member 17 is also rotated.

A rear closing member 21 is positioned at the rear end of the sleeve member 17. An elongated threaded member 22 threadably secures the closing member 21 to the rear end of the sleeve member 17. A nut 23 threadably secured to the sleeve member 17 locks the member 22 in position. By reason of the threaded interengagement of the parts, the axial extent of the closing member 21 relative to the sleeve member 17 may be adjusted.

Means is provided for supporting a sleeve member 17 so as to permit its rotation, such as a stand 24 carrying rollers 25 which rollingly engage and support the assembly of sleeve member 17 and threaded member 22.

A coupling member 26 is connected to and extends into the end member 21. This coupling member 26 is adapted to be connected to a source of compressed air, such as a tank or a compressor. A suitable swivel connection permits the connection of a hose to the coupling 26.

Extending through the closing member 21 from the coupling 26 is a long air passageway 27. This passageway 27 branches at its forward end to provide branching pas sageways 28 which communicate With the interior or bore of the sleeve member 17. Thus, there is communication provided for air between the coupling 26 and the bore of the sleeve member 17 in advance of the closing member 21.

The apparatus includes a mandrel which has a mandrel stem 29 and a mandrel plug 31. The rearwardmost end of the mandrel stem 29 has a threaded end 30 which is threadably engaged to and firm-1y secured to the forward end of the closing member 21 in advance of the passageways 28. The interconnection is such that the stem 29 rotates with the closing member 21. Thus it is seen that the sleeve member 17 and stem 29 rotate in unison.

The mandrel plug 31 of cylindrical shape is carried on the forward end of the stem 29. This plug 31 has an outer diameter complementary to the inner diameter of the tube in the final form thereof having the desired dimension. The diameter of the plug 31 is larger than 3 the diameter of the stem 29 so that there is a shoulder 34 at the junction of the plug 31 and the stem 29.

A piston member 32 is positioned within the sleeve member 17 and in close sliding fit with the stem 29. Annular seals 33 adjacent the opposite ends of the piston member 32 provide a good sealing engagement between the piston member 32 and the inner cylindrical wall of the sleeve member 17. The piston member 32 is arranged so that it may move longitudinally within the sleeve member 17 and in such a fit with the sleeve member 17 and stem 29 that leakage of air through the sleeve and past the piston member is prevented or minimized.

A metal tube, such as a copper tube, for example, is inserted into the apparatus by moving the tube from the left to the right in the views of FIGURES 1 and 2. In this insertion of the tube into the sleeve member 17, the three fin-rolling elements 11, 12, and 13 are moved away from each other and thus permit free movement of the tube through the path intermediate of the fin-rolling elements and into the forward end of the sleeve member 17. The tube in being inserted in the sleeve member 17 is slid over the mandrel to be concentric therewith. The tube in its condition prior to the forming of the helical fin thereon, and as shown in the drawing, is denoted by the reference character 35. The tube after the fin has been formed thereon, and as shown in the drawing, is denoted by the reference character 36. The helical fin provided on the tube by my invention is denoted. by the reference character 37.

A tube having the form of the unfinned tube 35 is pushed rearwardly into the sleeve 17 from the forward end of the apparatus when the fin-rolling elements are moved apart. Upon pushing of the unformed tube rearwardly in the sleeve member 17 and around the mandrel, the rear end of the tube engages the piston member 32 and pushes the piston member 32 rearwardly to a position adjacent the rear end of the sleeve member 17. The forward end of the unfinned tube is then positioned either between the fin-rolling elements or protruding a small distance in advance of the fin-rolling elements. In such a case, the tube will have a forward end portion which is a plain or unfinned. If the tube is moved farther back, so as to be positioned for complete fin-fo-rming throughout its length, then it will not have this plain end portion.

For the forming of the helical on the unfinned. tube, the three elements are moved toward each other and toward the tube to the position illustrated in FIGURES 1 and 2. The tin-rolling elements are then rotated and the sleeve member 17 is also rotated by the motor 19. The interaction of the disks of the plurality of finrolling elements on the outer wall of the tube, both by reason of inward radial pressure and the rotation of the fin-rolling elements, causes the metal of the tube to flow outwardly between the disks 15 and thus to coin or flow the metal outwardly to form the helical fin.

In the usual fin-forming apparatus and not utilizing my invention, the rotating fin-rolling elements not only form the fin but they also feed or advance the tube forwardly intermediate the fin-rolling elements. This feeding or advancing action causes the disks of the fin-rolling elements to adversely work the metal of the fin on the side from which the tube is fed forwardly by the rotating finrolling elements. This screw action provided by the interaction of the disks of the fin-rolling elements and the helical fin, wherein the forward feeding or advancing is done entirely by the rotating fin-rolling elements, causes undesirable formations in the tube and distortions in the grain structure of the tube and particularly in the fin portion of the tube.

By the use of my apparatus and the method, auxiliary means is provided for advancing or feeding the tube along its path intermediate the fin-rolling elements during the tin-forming operation. In the embodiment illustrated, pneumatic means is provided for pushing the tube forwardly of the apparatus and intermediate of the fin-rolling elements during the 'fin-forming operation. For this advancing of the tube, compressed air is connected to the coupling 26 so as to introduce compressed air into the bore of the sleeve member 17 rearwardly of the piston member 32. The compressed air pushes the piston member 32 forwardly, which in turn pushes the tube 35 forwardly so as to advance the tube as it moves through the fin-rolling operation. This relieves the feeding operation performed by the disks of the fin-rolling elements so that the pressure in a longitudinal direction of the disks upon the driven side of the fin is obviated or greatly diminished. By reason of this auxiliary feeding of the tube, the undesirable characteristics given to the tube and fin by apparatus not having my auxiliary feeding means are eliminated or greatly reduced.

Inasmuch as compressed air is resiliently yieldable, it is a preferred form of providing auxiliary means for feeding a tube forwardly. It is an impositive form of force as distinct from a positive form of force, such as provided in a direct mechanical -way. Should the auxiliary feeding performed by the compressed air be in excess of the rate of forward feeding permitted by the disks 15 interlocked with the helical fin, the compressed air resiliently yields so as to not overfeed or push the tube beyond that rate of forward movement normally permitted by the disks 15 engaged with the fin 37. Sufficient compressed air at required pressure is fed into the sleeve member 17 through the coupling 26 so as to urge the tube forwardly at a rate sufficient to substantially relieve the mechanical forward feeding that would be done by the disks pressing against the side of the fin in the absence of auxiliary feeding means. Danger of overfeeding by the auxiliary means is minimized or prevented by the resilient yieldability of the compressed air. Suitable valves are provided for introducing the compressed air into the sleeve member 17 and for exhausting the compresed air therefrom. When another unfinned tube is pushed back rearwardly into the sleeve member 17, compresed air is exhausted from the sleeve member 17 by opening a valve so that the piston member 32 does not work against compressed air during its return movement in the sleeve member 17.

It is to be noted that the stem 29 rotates with the sleeve member 17 which is rotated as the fin-rolling elements are rotated. The rotation of the disks 15 against the outer wall of the tube imposes not only a radial inward thrust on the tube but also a force which is circumferential and tends to turn the tube. This causes the tube to slidably engage the mandrel plug 31 within the tube to thus provide a wiping action of the tube against the mandrel plug 31. The internal bore of the tube is trued to have an accurate cylindrical wall by reason of this circumferential slide or wiping of the tube against the mandrel plug 31. A desirable effect is therefore accomplished by having the plug 31 so carried as to rotate with the sleeve 17 rather than having the plug 31 idle and free to rotate independently of the sleeve member 17.

It is also to be noted that the mandrel plug 31 extends substantially forwardly of the plurality of fin-rolling elements so as to support and maintain the tube in straight alignment after it leaves the fin-rolling elements. This tends to prevent kinking or cork-screwing of the tube as it leaves the fin-rolling elements after having the helical fin formed thereon. The structure and arrangement of the mandrel improves the character of the finished tube having the fin formed thereon. The shoulder 34 at the juncture of the mandrel plug 31 and mandrel stem '29 provides a stop for the piston member 32 so that the piston member 32 is not moved forwardly by compressed air beyond the limit provided by the shoulder 34.

Detail of the improved internal and external structure of the metal of a tube finned according to my invention is illustrated in FIGURE 5. The side of the fin denoted by the reference character 40 is the side which is referred to as the driven side of the fin, because this is the side driven side 40a.

that would be pressed in a longitudinal direction by mechanical forward feeding of the tube by the disks of the fin-rolling elements as they rotate in the fin-rolling operation. The outer end wall of the fin is denoted by the reference character 41. The outer tube wall at the root of the tube, that is, intermediate of the fin sections, is denoted by the reference character 42. The inner surface of the tube wall is denoted by the reference characetr 43. The undriven side of the fin, that is, the side opposite of the driven side, is indicated by the reference character 44 and the curved surface joining the root portion 42 and the side of the fin is indicated by the reference character 45.

In FIGURE 5, the grain structure is indicated by the stippling, and the strain lines in the grain structure, which is imparted to the metal by the fin-rolling operation, is shown by the darker stippling indicated in the sectional view. It is seen that the fin 37 of a tube made in accordance with my invention and as illustrated in FIG- URE 5 has the strain lines symmetrically arranged in the fin and in the tube wall on each side of the fin. It is also noted that the surface of the metal at the root 42 is disposed in a gradual and regular curve and also that the surface adjoining the root 42 and the side 44 is in a gradual and regular smooth curve sweeping upwardly to the side 44, this curve being. indicated at 45 of FIG- and the fin formed thereon and made without the use of my invention is illustrated in FIGURE 4.

It is here noted that the driven side indicated by the reference character 40a shows the grain structure to have been worked and distorted. Also the strain lines in the grain structure as indicated by the dark stippling are irregular and unsymmetrical, as compared with those shown in FIGURE 5. The end wall indicated by the reference character 41 is concave and irregular. The undriven side 44a is dissimilar in character with that of the The surface at the root, as indicated at 42-a, is irregular and not disposed in a smooth gradual curve. Also there is a pip or irregularity 45-0 at the surface intermediate the root 42-11 and the undriven side 44a. Some of the internal strain lines of the grain structure are directed to and terminate at the pip or irregularity 45-a. Instead of the smooth regular and sweeping curve at 45 and having strain lines disposed generally through that curve, as shown in FIGURE 5, the structure shown in FIGURE '4 has distortion and irregularity of surface and internal grain structure. Also the grain structure and strain lines at the internal wall surface are irregular and distorted, as illustrated by the comparison of FIGURE 4 with FIGURE 5.

The tube and fin structure illustrated in FIGURE 4 is relatively weak and brittle compared with that illustrated in FIGURE 5. The fin 37-a of FIGURE 4 may be easily fractured or displaced and its outer end wall 41-a is ragged and sharp in comparison with the smooth and flat outer wall 41 of the fin 37 shown in FIGURE 5.

Tubes made in accordance with my invention and emtion.

Although this invention has been described in its preferred form and preferred practice with a certain degree of particularity, it is understood that the present disclosure of the preferred form and preferred practice has been made only by way of example and that numerous changes of parts and steps may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

What is claimed is:

1. Apparatus for providing helical fins on the outer wall of a metallic cylindrical member comprising in combination a plurality of rotatable fin-forming elements disposed to form helical fins in a said cylindrical member moving intermediate said elements, guide means for guiding said cylindrical member in forming position intermediate said elements, said elements in forming said helical fins exerting a forward driving force upon the fins formed on said cylindrical member to feed the same forwardly of the apparatus intermediate of said elements, and pneumatic feeding means feeding said cylindrical member forwardly along the guide means and intermediate of said elements during the forming of fins on the cylindrical member by said elements to diminish the said forward driving force exerted upon said fins by said elements.

2. Apparatus for forming a helical fin on a metallic round member with minimum working of the metal in the fin during the forming of the fin, comprising in combination first means for guiding a said round member along a path, rotatable second means for rolling an integral helical fin from the outer wall of the round member as the round member is moved along said path, said second means interacting with said fin to feed, and to permit the feeding of, the round member forwardly along said path at a predetermined rate dependent on the rotative speed of said second means, and third means for feeding the round member forwardly throughout the operation of the rolling of said fin by the said second means continuously to assist the feeding by said second means, said third means yielding during said feeding to the rate of feeding permitted by said second means to not exceed the said rate of feeding.

3. Apparatus for forming a helical fin upon a metal tube comprising the combination of a plurality of rotatable fin-forming elements for causing metal of the tube to flow therefrom into a helical fin upon the rotation of the elements and the movement of the tube forwardly in a path intermediate of said elements, said elements in forming said fin also mechanically driving, by interaction of said elements and helical fin, the said tube forwardly in the apparatus to progressively feed the tube, at a rate dependent on the rotation of said elements, through said path and intermediate said elements, a pusher device adapted to engage and push the tube along said path and intermediate said elements throughout its travel during the operation of forming the fin thereon, and pneumatic means operating simultaneously with the forming of the said fin by said elements for exerting pneumatic force upon said pusher device to feed the tube forwardly intermediate said elements, said pneumatically powered pusher device relieving the force of said mechanical driving of the tube during the forming of the fin to minimize the working of the 'metal of said fin by said elements, the resiliency of said pneumatic means providing for the resilient yielding of the pusher device'to the maximum rate of feeding permitted by the interaction of said elements and helical fin. v

4. Apparatus for rolling a helical fin from the outer cylindrical wall of an elongated round member, comprising rotative rolling elements disposed at spaced locations about a reference line and arranged to roll a helical fin on a said round member moved forwardly along said reference line intermediate said elements, said elements interacting with said round member to advance the round member by screw action of the elements rotated in engagement with the helical fin, guiding means for guiding the round member along said reference line and substantially concentric therewith, and pneumatic pushing means guided by said guiding means for pushing said round member substantially throughout its travel along said reference line and intermediate said rolling elements for said fin-rolling thereon, said pushing means exerting a force continuously during the advancing of said round member by said elements in addition to the force advancing the round member exerted by said elements.

5. Apparatus for rolling a helical fin from the outer cylindrical wall of an elongated round member, comprising rotative rolling elements disposed at spaced locations about a reference line and arranged to roll a helical fin on a said round member moved forwardly along said reference line intermediate said elements, said elements interacting with said round member to advance the round member by screw action of the elements rotated in engagement with the helical fin, guiding means for guiding the round member along said reference line and substantially concentric therewith, and pneumatic pushing means guided by said guiding means for pushing said round member substantially throughout its travel along said reference line and intermediate said rolling elements for said fin to roll thereon, said pushing means exerting a force continuously during the advancing of said round member by said elements in addition to the force advancing the round member exerted by said elements, said pushing means being resiliently yieldable to resistance offered by the elements to longitudinal advancement of the round member beyond the rate of advancement provided by said screw action to assure that the round member is not longitudinally advanced at a rate greater than the rate of longitudinal advancement provided by said elements in forming the helical fin thereon.

6. Apparatus for forming a helical fin on the outer wall of a metal tube comprising in combination a plurality of rotative fin-rolling elements spaced and arranged to roll a said helical fin upon a tube longitudinally moved in a path intermediate said elements, said elements being disposed to apply a screw-driving force to said tube, a sleeve member for supporting said tube and guiding said tube to fin-forming position in said path intermediate of said elements, a piston member slidably mounted in said sleeve for advancing said tube through the sleeve member and through said path concurrently with the rolling of said fin by said elements, and resiliently yieldable actuating means carried by the sleeve member for actuating said piston member to move the same forwardly in the sleeve member for advancing said tube through the fin-rolling operation by said elements, said actuating means relieving the screwdriving force on the said tube by said elements and yielding to accommodate the actuation by the actuating means to the movement permitted by the said screw-driving force.

7. Apparatus for forming a helical fin on the outer wall of a metal tube comprising in combination a plurality of rotative fin-rolling elements spaced and arranged to roll a said helical fin upon a tube longitudinally moved in a path intermediate said elements, said elements being in inter-locked engagement with the said fin during the rolling of said fin, a sleeve member for supporting said tube and guiding said tube to fin-forrning position in said path intermediate of said elements, a piston member slidably mounted in said sleeve for advancing said tube through the sleeve member and through said path, and compressed air means adapted to advance said piston member forwardly along the sleeve member for advancing said tube past said elements to yieldingly feed the tube through the fin-rolling operation by said elements to the degree permitted by the inter-locked engagement of the said elements with said fin.

8. Apparatus for forming a helical fin on the outer cylindrical wall of a metal tube comprising the combination of fin-rolling means adapted to be positioned adjacent said tube and rotated relative to the tube to roll a helical fin thereon, the said tube being longitudinally advanced by said finrolling means pressing forwardly upon a side of the formed helical fin in the absence of auxiliary advancing means, a sleeve member disposed rearwardly of said fin-rolling means for supporting said tube relative to said fin-rolling means and guiding the tube toward said finrolling means, means for rotating said sleeve member and said fin-rolling means during the fin-rolling operation, a mandrel disposed along the axis of the sleeve member and having a cylindrically-shaped mandrel plug and a mandrel stem, said mandrel plug extending forwardly substantially beyond the said fin-rolling means to maintain the alignment of the tube with the axis of the sleeve member after the forming of the fin by said tin-rolling means, and auxiliary resiliently yieldable advancing means carried by the said sleeve member for continuously advancing the tube through the apparatus during said fin-rolling operation for minimizing the said pressing on a side of said fin by said fin-rolling means.

9. Apparatus for forming a helical fin on the outer cylindrical wall of a metal tube comprising the combination of fin-rolling means adapted to be positioned relative to a said tube and rotated relative to the tube to roll a helical fin thereon, a sleeve member disposed rearwardly of said fin-rolling means for supporting said tube relative to said tin-rolling means and guiding the tube toward said finrolling means, means for rotating said sleeve member and said fin-rolling means during the fin-rolling operation, a mandrel disposed along the axis of said sleeve member and having a cylindrically-shaped mandrel plug and a mandrel stern, said mandrel plug extending forwardly of said sleeve member to be disposed concentrically of the tube to engage the inner wall of said tube for receiving radial thrust imposed on the wall of said tube by said finrolling means, said mandrel stem extending rearw-ardly through said sleeve member, support means carried by said sleeve member for supporting said mandrel stem adjacent its rearward end, connecting means interconnecting said mandrel stem and sleeve member to cause said mandrel to rotate with said sleeve member to provide that circumferentially directed force exerted on the outer wall of said tube by said fin-rolling means rotating relative to said tube is slidably opposed by the said mandrel engaging the inner walls of said tube and so constructed and arranged that said tube is revolved about its axis against said mandrel to true the said inner wall to cylindrical shape during the fin-rolling operation, and compressedair means for yieldingly advancing said tube through said sleeve member and along said mandrel during the rotation of said sleeve member, said mandrel and said -fin-rolling means.

10. Apparatus for forming a helical fin on the outer cylindrical wall of a metal tube comprising the combination of fin-rolling means adapted to be positioned relative to a said tube and rotated relative to the tube to roll a helical fin thereon, a sleeve member disposed rearwardly of said fin-rolling means for supporting said tube relative to said fin-rolling means and guiding the tube toward said fin-rolling means, means for rotating said sleeve member and said fin-rolling means during the fin-rolling operation, a mandrel disposed along the axis of said sleeve member and having a cylindrically-shaped mandrel plug and a mandrel stem, said mandrel plug extending forwardly of said sleeve member to be disposed concentrically of the tube to engage the inner wall of said tube for receiving radial thrust imposed on the wall of said tube by said fin-rolling means, said mandrel stem extending rearwardly through said sleeve member, support means carried by said sleeve member for supporting said mandrel stem adjacent its rearward end, connecting means interconnecting said mandrel stem and sleeve member to cause said mandrel to rotate with said sleeve member to provide that circumferentially directed force exerted on the outer wall of said tube by said fin-rolling means rotating relative to said tube is slidably opposed by the said mandrel engaging the inner walls of said tube and so constructed and arranged that said tube is revolved about its axis against said mandrel to true the said inner wall to cylindrical shape during the fin-rolling operation, and a resiliently yieldable fluid-actuated piston disposed in said sleeve member around said mandrel stem and arranged to move along said sleeve member to push the tube toward and along said fin-rolling means during the rotation of said sleeve member, said mandrel and said tin-rolling means. 7

11. Apparatus for forming a helical fin on the outer cylindrical wall of a metal tube comprising the combination of fin-rolling means adapted to be positioned relative to a said tube and rotated relative to the tube to roll a helical fin thereon, a sleeve member disposed rearwardly of said fin-rolling means for supporting said tube relative to said fin-rolling means and guiding the tube toward said fin-rolling means, means for rotating said sleeve member and said fin-rolling means during the finrolling operation, a mandrel disposed along the axis of said sleeve member and having a cylin-drically-s'haped mandrel plug and a mandrel stern, said mandrel plug extending forwardly of said sleeve member to be disposed concentrically of the tube to engage the inner wall of said tube for receiving radial thrust imposed on the wall of said tube by said fin-rolling means, said mandrel plug also extending substantially (forwardly of said fin-ro lling means to hold in straight cylindrical form the wall of said tube advancing from said fin-rolling means, said mandrel stem extending rearwardly through said sleeve member, support means carried by said sleeve member for supporting said mandrel stem adjacent its rearward end, connecting means interconnecting said mandrel stem and sleeve member to cause said mandrel to rotate with said sleeve member ltO provide that circumferentially directed force exerted on the outer wall of said tube by said fin-rol'ling means rotating relative to said tube is slidably opposed by the said mandrel engaging the inner wall of said tube and so constructed and arranged that said tube is revolved about its axis against said mandrel to true the said inner Wall to cylindrical shape during the fin-rolling operation, and pneumatic means for pushing the tube through the sleeve member toward and along the finro'lling means during the rotation of said sleeve member, said mandrel and said fin-rolling means to relieve the forward pressure imposed on the helical fin by said finrolling means, said pneumatic means including a piston movable along said mandrel stem. and means for introducing compressed air into the sleeve member rearwardly of said piston.

12. In apparatus having rotative fin-rolling means adapted to roll a helical fin on a metal tube by applying a radially inward directed force and a circumferentially directed force upon said tube, the combination of yieldable feeding means for advancing a said tube toward the fin-rolling means, rotative support means for accommodating the tube therein and guiding the tube toward the fin-rolling means, rotative mandrel means adapted to be positioned in the tube for engaging and supporting the inner wall of the tube radially inward of the finrolling means in opposition to said radially inward directed force, and actuating means for the simultaneous rotating of said fin-rolling means, said support means and said mandrel means and simultaneously operating said feeding means so constructed and arranged that the said circumferentially directed force on said tube presses the tube circumferentially relative to and against the mandrel means to true the said inner wall to cylindrical form during the feeding of the tube by said feeding means, said feeding means yieldably accommodating the rate of feeding to the interaction of the fin-rolling means and the fin rolled on said tube.

13. The method of forming a helical fin on a metal tube which comprises rolling a helical fin on the said tube by helical fin-rolling means and concurrently resiliently urging the tube through the helical fin-rolling means at a rate not in excess of the rate of forward feed provided by said fin-rolling means.

14. The method of forming a helical fin on a metal tube which comprises rolling a helical fin on the said tube by helical fin-forming means and concurrently applying a resiliently yieldable force to the end of the tube to advance the tube through helical fin-forming means, said force resiliently yielding to resistance to forward advancing of the tube beyond the rate of advancement provided by the said helical fin-forming means.

15. In the forming of a fin on a metallic tube by extruding metal of the tube outwardly .by rotating discs which discs mechanically feed the tube forwardly and exert a pressure on a side of the fin in the extruding operation, the process of rolling a helical fin on said tube by said rotating discs, and resiliently feeding the tube forwardly along the said discs during said mechanical feeding of the tube, and adjusting the rate of the said resilient feeding relative to the rate of the mechanical feeding by said discs to reduce the pressure on the side of the fin by said discs in said extruding operation.

16. In the operation of fin-forming on a metallic tube by rotating discs extruding metal outwardly and mechanically feeding the tube forwardly by mechanical pressure on the rearward side of the fin by the rotating discs, the process of rolling a helical fin on said tube by said rotating discs, and yieldably urging the tube forwardly during the forming of the fin by said discs at a rate not in excess of the rate of forward mechanical feed by said discs.

17. In the operation of fin forming on a metal tube by rotating discs in engagement with said tube which discs force metal radially outwardly on the tube and simultaneously mechanically feed the tube forwardly by pressing on the rearward side of the fin, the process of rolling a helical fin on said tube by said rotating discs, and providing an auxiliary force feeding said tube forwardly during the fin-forming by said discs to reduce the pressure by said discs on the rearward side of the fin, and of yielding said auxiliary force to the resistance of said discs in engagement with said tube to limit the rate of forward feed of the tube to the rate of said mechanical forward feed provided by said rotating discs.

References Cited by the Examiner UNITED STATES PATENTS 1,761,981 6/1930 'Bundy 257262.21 1,865,575 7/1932 Locke 13 2,358,307 9/1944 Dewey 8013 2,508,517 5/1950 Hill 80-62 2,562,785 7/1951 Hill 257262.21 2,586,653 2/1952 Hill 8062 2,680,975 6/1954 Goldsmith 8013 FOREIGN PATENTS 111,528 9/ 1940 Australia.

CHARLES W. LANHAM, Primary Examiner. LEON PEAR, WILLIAM J. STEPHENSON, Examiners.

J. E. SCHARDT, C. H. HITTSON, G. P. CROSBY,

Assistant Examiners. 

1. APPARATUS FOR PROVIDING HELICAL FINS ON THE OUTER WALL OF A METALLIC CYLINDRICAL MEMBER COMPRISING IN COMBINATION A PLURALITY OF ROTATABLE FIN-FORMING ELEMENTS DISPOSED TO FORM HELICAL FINS IN A SAID CYLINDRICAL MEMBER MOVING INTERMEDIATE SAID ELEMENTS, GUIDE MEANS FOR GUIDING SAID CYLINDRICAL MEMBER IN FORMING POSITION INTERMEDIATE SAID ELEMENTS, SAID ELEMENTS IN FORMING SAID HELICAL FINGS EXERTING A FORWARD DRIVING FORCE UPON THE FINS FORMED ON SAID CYLINDRICAL MEMBER TO FEED THE SAME FORWARDLY OF THE APPARATUS INTERMEDIATE OF SAID CYLINDRICAL AND PNEUMATIC FEEDING MEANS FEEDING SAID CYLINDRICAL MEMBER FORWARDLY ALONG THE GUIDE MEANS AND INTERMEDIATE OF SAID ELEMENTS DURING THE FORMING OF FINS ON THE CYLINDRICAL MEMBER BY SAID ELEMENTS TO DIMINISH THE SAID FORWARD DRIVING FORCE EXERTED UPON SAID FINS BY SAID ELEMENTS. 